Attachment of workpieces on a lathe

ABSTRACT

A kit for use in attaching and securing workpieces comprising hubless brake drums and rotors of various sizes on a lathe includes an arbor mount comprising a substantially cylindrical tube portion with an enlarged terminal member at one end. The arbor mount has a central bore adapted to receptive the shaft of the lathe. The kit also includes a pair of backing plates which can acommodate various sized workpieces. Each plate has a central hole with a diameter of sufficient size so that the tube portion of the arbor mount may pass therethrough. The first side of each plate is adapted to receive the terminal member of the arbor mount, and each plate is adapted to be positioned over the tube portion of the arbor mount with the terminal member behind a workpiece. The kit also includes a pair of centering cones which can accommodate various sized workpieces. Each of the cones has a central bore which is adapted to receive the tube portion of the arbor mount in sliding engagement therewith, and to be positioned over the tube portion of the arbor mount with the smaller end of the cone preceding its larger end and secured against the end wall of a workpiece. The kit also includes a compression cup for use with one of the plates and one of the cones. This cup has a base portion and a sidewall, and the base portion has a central hole that is adapted to receive the tube portion of the arbor mount. The sidewall terminates in a peripheral edge that is located so as to correspond with the periphery of one of the plates. The cup is adapted to be positioned and secured over the arbor mount so that compressive forces may be applied to the end wall of a workpiece between the peripheral edge of the sidewall of the cup and the periphery of the plate. A nut is used to secure a cone or the cup on the tube portion of the arbor mount.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of the application entitled"Work Holder Assembly For A Lathe" which was filed Jul. 15, 1996 andassigned a serial number of Ser. No. 08/680,458, now U.S. Pat. No.5,737,985, the disclosure of which is fully incorporated herein byreference.

FIELD OF INVENTION

This invention relates to lathes having rotary driven shafts that areused to machine workpieces having an end wall with a central holetherein, such as brake drums and rotors. More specifically, theinvention relates to a kit of components that may be used in connectionwith such lathes to hold workpieces of a variety of sizes and end wallthicknesses, and having central holes of various sizes, such that theend wall of the workpiece held thereby is maintained in a positionsubstantially perpendicular to the axis of rotation of the shaft.

BACKGROUND OF THE INVENTION

Generally, a vehicular brake is a mechanical device for retarding themotion of the vehicle by means of friction. These brakes use frictionbetween brake surfaces that turn with the wheels and friction pads thatare stationary with respect to the turning wheels to convert the kineticenergy of the moving vehicle into heat. There are tremendous forcesinvolved in braking a vehicle, and these forces can result in thegeneration of considerable heat during braking, as well as the wear ofthe friction surfaces and pads of the brakes. Wear may be acceleratedby, among other things, dirt or dust that may infiltrate the brakeassembly and migrate to locations between the pads and the frictionsurfaces. In addition, because the friction pads in use today are nolonger made with asbestos, a superior heat-dissipating material,accelerated wear due to the effects of high heat generation is morecommon than in the past.

Vehicles are generally equipped with drum-type or disc-type brakes. Mostvehicles in use today are provided with disc-type brakes on at least thefront wheels, and sometimes on all four wheels. Drum-type brakes weremore commonly used in the past than they are today, but they are stillutilized on the rear wheels of a significant number of vehicles.

Disc-type brakes operate by forcing friction pads (brake linings)against both sides of a rotating disc-shaped rotor. This rotor turnswith the wheel of the vehicle and within a stationary housing called thecaliper assembly. When the brakes are applied, hydraulic fluid causespistons in the caliper assembly to push the friction pads against therotating disc-shaped rotor, thereby retarding the motion of the vehicle.

The rotor is generally comprised of a pair of annular metal discs joinedtogether by a plurality of spacers that are arranged so as to maximizethe heat-dissipating area of the annular discs. The annular discs aresupported by a central end wall which is disposed generally parallel tothe discs. This end wall, which is typically joined to the discs by ashort connecting sidewall, generally has a central hole to accommodatethe spindle on which the associated wheel is mounted, and a plurality ofbolt holes to accommodate the lug bolts or studs that are used to mountthe wheel to the vehicle. Early rotors of disc-type brake systems wereprovided with a hub or raised collar around the central hole in the endwall. More recently, however, hubless rotors have been used, which arecharacterized by a substantially flat end wall. Many hubless rotors areof a unitary construction, wherein the end wall, adjacent sidewall andone of the annular discs are formed from a single piece of metal. Otherhubless rotors are of a composite construction, wherein the end wall andadjacent sidewall are formed from a separate, usually considerablythinner, piece of metal from those which form the annular discs.

Drum-type brakes include a metal brake drum which rotates with thewheel. The drum has an internal cylindrical friction surface againstwhich brake shoes, equipped with friction pads (brake linings), havingarcuate external surfaces that correspond to the internal surface of thedrum, are pushed by the action of a piston.

A brake drum is comprised of an end wall, around which is disposed adepending sidewall, the internal surface of which serves as the frictionsurface. This end wall generally has a central hole to accommodate thespindle on which the associated wheel is mounted, and a plurality ofbolt holes to accommodate the lug bolts or studs that are used to mountthe wheel to the vehicle. Early brake drums were provided with a hub orraised collar around the central hole in the end wall. More recently,however, hubless drums have been used, which are characterized by asubstantially flat end wall. Some hubless drums, like rotors, are of aunitary construction, wherein the end wall and the adjacent sidewall areformed from a single piece of metal. Most hubless drums, however, are ofa composite construction, wherein the end wall is formed from aseparate, usually considerably thinner, piece of metal from that whichforms the adjacent sidewall.

Brake drums and rotors can vary considerably in size, dependingprimarily on the size and weight of the vehicle that they must stop. Thecenter hole sizes in the end walls of the drums and rotors can also varyin size, to accommodate spindles of various sizes. Typically, the largerand heavier the vehicle, the larger the drum or rotor and spindle, andthe larger the center hole in the end wall of the drum or rotor. Inrecent years, so-called "super-duty" braking systems have been developedfor busses and large trucks. The drums and rotors of such super-dutysystems are correspondingly larger and heavier than the drums and rotorsof passenger cars and light trucks, and they are generally of unitaryconstruction. Although the outside diameter of hubless brake drums androtors can vary across a considerable range, such workpieces willtypically have end wall center hole diameters that vary within a rangeof about 2.50 inches to about 5.75 inches.

Wear, misuse or improper maintenance of brake drums and rotors can leadto damage, such as warping or the development of grooves or scoring inthe friction surfaces. Such surface damage will reduce the effectivenessof the brakes by reducing the areas of such surfaces that are placedinto contact with the friction pads to slow the vehicle. Warping,grooves and scoring in worn brake discs and drums may generally beremoved, however, if not too deep or extensive, to restore full functionto the brakes. Since rotors and drums have a significant value, refacingof the friction surfaces is economically preferably to replacement, ifit can be accomplished at a reasonable cost.

A brake rotor or drum is generally removed from the vehicle and mountedon a lathe to machine or reface its friction surface or surfaces.Typically, a lathe for machining brake drums and rotors is equipped witha rotating shaft, sometimes referred to as a spindle or an arbor, onwhich the workpiece may be mounted, and a slide assembly on which acutting or grinding tool may be mounted. Generally, the shaft has athreaded portion at its outer end, which shaft is insertable through thecentral hole in the end wall of a brake drum or rotor in order tofacilitate mounting of such workpiece thereon. As the workpiece isturned on the shaft, the cutting or grinding tool is advanced, eitherautomatically or manually, into engagement with the workpiece to trim orshave metal therefrom until the desired dimension and surface finish areobtained.

It is essential that the workpiece be mounted in a secure fashion on thelathe so that the end wall of the workpiece may be maintained in aposition substantially perpendicular to the axis of rotation of theshaft while the workpiece is being machined. This will insure that thefriction surface or surfaces of the workpiece will be maintained in anunvarying position relative to the cutting or grinding tool as theworkpiece is rotated on the shaft, so that machining of the frictionsurface or surfaces may produce a smooth finish. However, since brakedrums and rotors are provided in a variety of sizes to fit a variety ofcars and other vehicles, the end walls of such workpieces may vary indiameter and thickness, and the central hole therein may also vary indiameter. Therefore, it is also desirable that the lathe mounting systemfor such workpieces possess some flexibility or adaptability to permitthe mounting of workpieces having different physical configurations.Unfortunately, however, existing mounting systems have generally failedto combine security in mounting with adaptability to permit the mountingof workpieces of different types and configurations. Most of themounting systems that permit the mounting of differently sizedworkpieces achieve this adaptability through a use of many components,each of which is adapted for a particular drum or rotor configuration.Such systems, requiring a large number of components in order toaccommodate various configurations, are frequently too expensive for thesmall brake shop operator to justify.

It has been common practice to mount a workpiece on a lathe by securingit between or against one or more cones. The use of cones offers someflexibility in dealing with various center hole configurations, and italso permits the workpiece to be readily centered with respect to thecentral hole in its end wall. A workpiece having a hub around itscentral hole is typically mounted between two cones, each having acylindrical bore therethrough, that are slidably mounted on the shaft ofthe lathe with the smaller ends thereof facing together and protrudinginto opposite sides of the hub. A hubless drum or rotor is frequentlymounted using a single such cone that is employed in combination withother components. Typically, the cone is placed on the shaft with itssmaller end facing the workpiece, and this smaller end of the cone isinserted into the central hole of the workpiece. A backing component mayalso be employed on the side of the workpiece opposite the cone, so thatthe workpiece will be held between the cone and the backing component.Thus, the cone and its backing component cooperate with the central holein the end wall of the workpiece to align and hold the workpiece on thelathe.

An example of such a mounting system is described in U.S. Pat. No.4,708,041 of Granger. The system of Granger employs a cone having acylindrical bore therethrough, which cone is adapted to slide over acylindrical tubular component having an enlarged cylindrical terminationat one end thereof. This component, which Granger refers to as aroto-hub, also has a hollow cylindrical recess having a squarecross-section within its termination at the junction of the cylindricaltermination and the tubular portion. The roto-hub is mounted on theshaft of a lathe, and the drum or rotor to be machined is placedthereover. The cone, which has a small end and a large end, is then slidover the cylindrical tubular portion of the roto-hub so that its smallend is received within the cylindrical recess in the cylindricaltermination. However, the workpiece is secured on the shaft only byfriction between the inside surface of the cone and the outside surfaceof the tubular portion of the roto-hub.

A similar mounting system to that of Granger, but one that isspecifically designed for use in connection with hubless drums andunitary hubless rotors, is manufactured and sold by RELS ManufacturingCompany of Rockford, Minn. This system is designed to fit over the arboror shaft of a lathe. It includes a center locator comprising asubstantially cylindrical tube portion having an enlarged cylindricalterminal member at one end. The center locator has a central bore thatis adapted to receive the shaft in sliding engagement therewith, and theaxis of the central bore is substantially coincident with the axis ofthe tube portion of the center locator. The tube portion has an outsidediameter that is smaller than the diameter of the central hole in theend wall of the drum or rotor, and the terminal member of the locator islarger than said central hole. The system also includes a cone having alarge base end and a smaller opposite end and a central boretherethrough such that the axis of the central bore is substantiallycoincident with the axis of the cone, said bore being adapted to receivethe tube portion of the center locator in sliding engagement therewith.The cone has a diameter at its base end that is larger than the diameterof the central hole in the end wall of the drum or rotor. The terminalmember also has a beveled surface extending radially outwardly from itsjunction with the cylindrical tube portion of the center locator. Thisbeveled surface is disposed at an angle similar to that of the conicalsurface of the cone, so that the workpiece may be positioned over thecenter locator and the cone may be positioned over the tube portion ofthe center locator, with its smaller end preceding its base end andprotruding through the central hole in the end wall of the workpiece toengagement with the beveled surface of the terminal member. A spacer maybe placed over the cylindrical tube portion of the center locator, ifnecessary, and a nut is threaded over external threads on the outer endof the locator to hold the assembly in place. Similar or identicalsystems are made and sold by several manufacturers besides RELS, but forsimplicity, a system of this type will be referred to herein as the RELSsystem. One advantage of the RELS system over the system of Granger isthe fact that the nut of the RELS system more securely holds the cone inplace against the end wall of the workpiece than does the frictionalengagement between the cone and the roto-hub of Granger.

The use of a cone and an associated backing member such as is employedby the Granger system or the RELS system for hubless drums and rotorsmay not prevent vibration of the workpiece as it is machined, because insuch a system, all of the force that is applied to hold the workpiecesecurely is applied in the vicinity of the central hole. When thecutting or grinding tool is applied to the friction surface or surfacesof a workpiece held by such a system, the forces applied by the tool ina direction parallel to the axis of rotation at a point some distanceaway from the central hole may be sufficient to cause deflection orvibration in the workpiece. This deflection or vibration will be morepronounced in workpieces of composite construction, having thinner endwalls than workpieces of unitary construction, and in fact suchcomposite workpieces may be distorted or deformed under the influence ofsuch forces. In addition, deflection or vibration in the workpiece,sometimes referred to as "chattering", precludes obtaining a smoothfinish on the friction surface or surfaces. Consequently, it hassometimes been considered advantageous to provide an additionalstabilizing force on the end wall of the workpiece itself in order tohold it securely with respect to the cutting or grinding tool.

One mounting system that provides such additional stabilizing force onthe end wall of the workpiece was especially developed for use inconnection with composite rotors by RELS Manufacturing Company ofRockford, Minn. This system employs a pair of circular plates instead ofa cone and backing plate to hold the workpiece on the shaft. The RELSsystem for composite rotors also utilizes the center locator and the nutand spacer of the RELS system for drums that is discussed hereinabove.However, instead of using a cone to align and hold the rotor on thelocator, this system uses a pair of plates, each of which is providedwith a central hole that is adapted for sliding engagement with thecenter locator. One of the plates is substantially flat, and the otherhas a raised ring around its central hole. This ring is precisely sizedto fit inside and to mate with the central hole in a particular rotor.Since each such plate has two sides or faces, one raised ring may beprovided on each side, but each such plate can then only accommodaterotors having two specific center hole sizes. It would be necessary tohave a plurality of such plates in order to be prepared to machinerotors having different center hole sizes.

Another means for providing an addition al stabilizing force on the endwall of the workpiece is described in U.S. Pat. No. 4,165,662 ofBesenbruch et al. The Besenbruch system has two embodiments, one forholding a drum and one for holding a rotor. In order to mount a drum,the Besenbruch system employs as a backing member an adapter having afront face with a conical recess and a central hole therethrough so thatthe adapter may be fit over the shaft of the lathe. After this adapterand the drum are placed over the shaft, a cone having a cylindrical boreand a small end and a large end is fitted over the shaft so that itssmall end protrudes through the central hole in the end wall of the drumand is received in the adapter. A circular, rigid, anti-chatter,aligning and straightening plate having a central hole to receive theshaft is then placed over the shaft in front of the drum. The plate isprovided with a plurality of threaded holes spaced therearound toreceive a plurality of adjustment bolts, which bear adjustably againstthe circular end wall of the drum. The shaft has a threaded hole in itsend, and a bolt is provided that mates with the threaded hole. Aplurality of spacers are placed over the bolt and the bolt is threadedinto the end of the shaft.

The Besenbruch system for rotors includes a pair of cones, each having acylindrical bore and a small end and a large end, as well as acylindrical adapter having a central bore and a conical end face. Onecone is fitted over the shaft so that its small end faces outwardly. Thecylindrical adapter is then placed over the shaft so that the small endof the first cone protrudes into its central bore, and the rotor isplaced in front of the adapter. The second cone is then placed over theshaft so that its small end protrudes through the central hole in theend wall of the rotor and is received in the cylindrical adapter. Acircular, rigid, anti-chatter, aligning and straightening plate that isessentially identical to the one employed for drums is then placed overthe shaft in front of the drum. The plate, like the one for drums, isprovided with a plurality of threaded holes spaced therearound toreceive a plurality of adjustment bolts, which bear adjustably againstthe circular end wall of the rotor. The shaft has a threaded hole in itsend, and a bolt is provided that mates with the threaded hole. Aplurality of spacers are placed over the bolt and the bolt is threadedinto the end of the shaft. When either of the Besenbruch systems areinstalled to hold a workpiece on a lathe, the various adjustment boltsmust each be adjusted to apply a stabilizing force to the end wall ofthe workpiece in order for the anti-chatter plate to be effective.Furthermore, it is frequently necessary to adjust the bolts, turn theworkpiece on the lathe to check for vibration and adjust the bolts againto eliminate it. Several adjustment steps may be required beforemachining of the workpiece can proceed.

Another means for providing a stabilizing force on the end wall of aworkpiece was devised primarily for use in connection with workpieces ofunitary construction, having relatively thick end walls. This mountingmeans employs a cone that is placed on the shaft with its small endprotruding into the central hole of the end wall of the workpiece, and apair of bell-shaped clamps that are placed on the shaft with their open"bell" ends facing the end wall, one on each side. A spring may also beplaced between one of the bell clamps and the cone to maintain the conein place in contact with the central hole in the end wall of theworkpiece. Suitable spacers are placed over the shaft outside the outerbell clamp and a nut is fastened onto the externally-threaded outer endof the shaft. The bell clamps are thereby secured in place on the shaft,each in contact with one side of the end wall of the workpiece, althoughgenerally, the configuration of the "bell" ends is such that only a partthereof will be in contact with the end wall.

This mean s of mounting a workpiece on the rotary shaft of a lathe maybe acceptable for use in mounting many brake drums and rotors of unitaryconstruction, because it applies a stabilizing force at several widelyseparated points on the end wall. However, such mounting means may notbe suitable for use with the newer drums and rotors of compositeconstruction. As has been mentioned, the thinner end walls of compositedrums and rotors are more likely to be subject to vibration anddeflection during machining than are the thicker end walls of workpiecesof unitary construction. Therefore, the bell clamps generally do notapply sufficient force on the thin end walls of composite workpieces tomaintain them in a stable position with respect to the cutting orgrinding tool. Consequently, the workpieces will be subject to vibrationor chattering, which precludes obtaining a smooth finish on the frictionsurface or surfaces.

In order to eliminate vibration and chattering in the end walls ofcomposite drums and rotors, it is necessary to apply a greater force tothe end walls than can readily be applied by the bell clamps, withoutcausing distortion of the shaft. As has been mentioned, the bell clampswere designed to provide a stabilizing force or forces to the end wallof a workpiece. They were not designed to provide a larger force, aclamping or compressive force, such as is generally required to preventor eliminate chattering. One reason that the bell clamps do not providesufficient force to hold the end walls is that they are fastened inplace by means of a nut that is threaded onto the externally-threadedouter end of the arbor or shaft. This arbor is generally designed sothat the nut on its threaded end may be used to hold a workpiece or anadapter in place thereon, but it is not generally suitable for theapplication of compressive forces to items mounted thereon. If it isdesired to tighten the nut so as to apply a compressive force thereby,care must be taken to avoid overtightening that warps the end of theshaft so that it is no longer properly aligned with its axis ofrotation. Another reason that the bell clamps do not provide sufficientcompressive force to hold the thin end walls is due to the wide spacingof the stabilizing forces which they apply to the end wall. As has beenmentioned, the bell clamps generally have gaps in their contactsurfaces, or the surfaces that contact the end wall of the workpiece.These gaps are designed to reduce the surface area in contact with theend wall so that the minimal force applicable through the tightening ofthe arbor nut will be translated into a sufficient force per unit areathat will serve to stabilize the workpiece on the arbor. However, thisstabilizing force is generally not sufficient to prevent vibration andchattering in workpieces having thin end walls as such workpieces aremachined. In addition, this stabilizing force is frequently inadequateto hold the workpiece securely so as to prevent it from slipping as itsfriction surface or surfaces are machined on the shaft.

It would be desirable, therefore, if a kit of components could bedeveloped that would be suitable for securing a workpieces comprisingbrake drums and rotors of unitary or composite construction on a lathehaving a rotary driven shaft, such that the end wall of the workpiece ismaintained in a position substantially perpendicular to the axis ofrotation of the shaft. It would also be desirable if such a kit could bedeveloped that would be suitable for mounting workpieces having avariety of end wall sizes and thicknesses, and having a variety ofcentral hole sizes, without requiring a separate adapter for each of thevarious sizes and end wall configurations. It would also be desirable ifsuch a kit could be developed that would be suitable for mounting bothdrums and rotors in the same or a similar fashion. It would also bedesirable if such a kit could be developed that is capable of applying acompressive force to the end wall of a workpiece, especially one ofcomposite construction, in order to eliminate vibration without the riskof warping the shaft of the lathe. It would also be desirable if such akit could be developed that would not require that several adjustmentsteps be taken to eliminate chattering in the end wall of the workpiece.It would also be desirable if such a kit could be developed that wouldbe compatible with existing systems for mounting of workpieces.

OBJECTS AND ADVANTAGES OF THE INVENTION

Accordingly, it is an object of the invention claimed herein to providea kit of components for securing workpieces, comprising hubless brakedrums and rotors of unitary or composite construction, each of which isprovided with an end wall having a central hole therein, on a lathehaving a rotary driven shaft, such that said end wall is maintained in aposition substantially perpendicular to the axis of rotation of theshaft. It is another object of the invention to provide a kit ofcomponents that is suitable for mounting workpieces having a variety ofend wall configurations and central hole sizes, without requiring aseparate adapter for each of the various sizes and configurations. It isyet another object of the invention to provide a kit of mountingcomponents that is suitable for mounting both drums and rotors in thesame or a similar fashion. Another object of the invention is to providesuch a kit that can be used to apply a compressive force to the end wallof a workpiece, especially one of composite construction, in order toeliminate vibration, without the risk of warping the shaft of the lathe.It is still another object of the invention to provide a kit of mountingcomponents that does not require that several adjustment steps be takento eliminate chattering in the end wall of the workpiece. It is also anobject of the invention to provide a kit of mounting components that iscompatible with the known RELS systems for mounting of rotors and drums,in that it employs some of the same components of the RELS systems.

Additional objects and advantages of this invention will become apparentfrom an examination of the drawings and the ensuing description.

SUMMARY OF THE INVENTION

The invention comprises a kit of components for use in attaching andsecuring on a lathe having a rotary driven shaft workpieces comprisinghubless brake drums and rotors of various sizes, each of which isprovided with an end wall with a central hole therein. By utilizing thecomponents of the kit, such workpieces may be attached and secured on alathe in a manner such that the end wall of the workpiece is maintainedin a position substantially perpendicular to the axis of rotation of theshaft. The kit includes an arbor mount comprising a substantiallycylindrical tube portion with an enlarged terminal member at one endthereof. The arbor mount has a central bore therethrough such that theaxis of the central bore of the arbor mount is substantially coincidentwith the axis of the tube portion, and the central bore of the arbormount is adapted to receive the shaft of the lathe in sliding engagementtherewith so that said arbor mount may be positioned over the shaft. Thekit also includes a pair of backing plates. A first backing plate has agenerally circular configuration with a first side and a second side anda central hole therethrough, which hole has a diameter that is greaterthan the outside diameter of the tube portion of the arbor mount so thatsaid tube portion will pass through the central hole of said firstbacking plate. The first side of the first backing plate is also adaptedto receive in mating relationship the terminal member of the arbormount. Consequently, the first backing plate is adapted to be positionedover the tube portion of the arbor mount in mating relationship with theterminal member thereof, behind a workpiece. A second backing plate hasa generally circular configuration with an outside diameter greater thanthat of the first backing plate. The second backing plate also has afirst side and a second side and a central hole therethrough, which holehas a diameter that is greater than the outside diameter of the tubeportion of the arbor mount so that said tube portion will pass throughthe central hole of the second backing plate. The first side of thesecond backing plate is adapted to receive in mating relationship theterminal member of the arbor mount, and the second backing plate isadapted to be positioned over the tube portion of the arbor mount inmating relationship with the terminal member thereof, behind aworkpiece. The kit also includes a pair of centering cones. The firstsuch cone has a larger end and a smaller end, and a central boretherethrough such that the axis of the central bore of said firstcentering cone is substantially coincident with the axis of the cone,said bore of the first centering cone being adapted to receive the tubeportion of the arbor mount in sliding engagement therewith. The firstcentering cone is adapted to be positioned over the tube portion of thearbor mount with its smaller end preceding its larger end and securedagainst the end wall of a workpiece. The second centering cone has alarger end and a smaller end and a central bore therethrough such thatthe axis of the central bore of said second centering cone issubstantially coincident with the axis of the cone. The bore of thesecond centering cone is adapted to receive the tube portion of thearbor mount in sliding engagement therewith, and the second centeringcone has a diameter at its larger end that is greater than the diameterat the larger end of the first centering cone. Like the first centeringcone, the second centering cone is adapted to be positioned over thetube portion of the arbor mount with its smaller end preceding itslarger end and secured against the end wall of a workpiece. The kit alsoincludes means for securing a centering cone on the tube portion of thearbor mount against the end wall of a workpiece, and a compression cuphaving a base portion and a sidewall extending from the peripherythereof. The base portion of the compression cup has a central holetherethrough that is adapted to receive the tube portion of the arbormount, and the sidewall terminates in a peripheral edge that is locatedso as to correspond with the periphery of the first backing plate. Thecompression cup is adapted to be positioned and secured over the arbormount so that compressive forces may be applied to the end wall of aworkpiece between the peripheral edge of the sidewall of the cup and theperiphery of the first backing plate. The kit also includes means forsecuring the compression cup over the arbor mount.

In order to facilitate an understanding of the invention, the preferredembodiments of the invention are illustrated in the drawings, and adetailed description thereof follows. It is not intended, however, thatthe invention be limited to the particular embodiments described or touse in connection with the apparatus illustrated herein. Variousmodifications and alternative embodiments such as would ordinarily occurto one skilled in the art to which the invention relates are alsocontemplated and included within the scope of the invention describedand claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of an assemblage of several ofthe components of the kit of the invention in a first embodiment thatmay be used to secure a workpiece on a lathe.

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1,illustrating its use in holding on the shaft of a lathe a workpiece ofcomposite construction and having a central hole in the end wall thereofthat is smaller in diameter than the diameter of the central hole in thebacking plate that is a component of the kit.

FIG. 3 is a cross-sectional view of the embodiment of FIG. 1,illustrating its use in holding on the shaft of a lathe a workpiece ofcomposite construction and having a central hole in the end wall thereofthat is larger in diameter than the diameter of the central hole in thebacking plate that is a component of the invention.

FIG. 4 is an exploded perspective view of an assemblage of several ofthe components of the kit of the invention in a second embodiment thatmay be used to secure a workpiece on a lathe.

FIG. 5 is a cross-sectional view of the embodiment of FIG. 4,illustrating its use in holding on the shaft of a lathe a workpiece ofunitary construction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention comprises a kit of components for use in attaching andsecuring on a lathe having a rotary driven shaft workpieces comprisinghubless brake drums and rotors of various sizes, each of which isprovided with an end wall with a central hole therein. The kit isadapted to attach and secure workpieces of either composite or unitaryconstruction, and having end wall holes of various diameters. By a useof the components of the kit, a workpiece may be secured in a mannersuch that its end wall is maintained in a position substantiallyperpendicular to the axis of rotation of the shaft. Some of thecomponents of the kit are especially adapted to mount workpiecescomprised of hubless brake drums and rotors of composite construction,as illustrated in FIGS. 1 through 3. Other components are especiallyadapted to mount workpieces of unitary or cast construction, includingthose of super duty braking systems, as shown in FIGS. 4 and 5.

The kit of components which comprise the invention, as illustrated inthe drawings, is designed to be utilized with an arbor, spindle or shaftof a lathe, and as used herein, the terms "arbor", "spindle" and "shaft"are considered to be interchangeable alternatives. The components of theinvention may be used on or in connection with a variety of lathes, oneof which, for example, is the brake lathe which is described and shownin U.S. Pat. No. 2,891,435 of Billeter. This lathe, which is well-knownand in common use, is manufactured and sold by Ammco Tools, Inc. ofNorth Chicago, Ill. For information about the operation and use of thislathe, reference is made to the aforementioned patent of Billeter.

Referring now to FIGS. 1 through 3, an assemblage of several of thecomponents of the kit of the invention is illustrated in a firstembodiment 10 that may be used to hold and secure on a lathe having arotary driven shaft (not shown) a workpiece of composite constructionand having a central hole in an end wall thereof. FIG. 2 shows thecomponents of the work holder assembly kit comprising embodiment 10 asthey may used in a cooperative fashion to hold a workpiece having acentral hole in its end wall of relatively small size, such as compositebrake rotor assembly 11A having end wall 12A. FIG. 3 shows thecomponents of the work holder assembly kit comprising embodiment 10 asthey may be used in a cooperative fashion to hold a workpiece having acentral hole in its end wall of relatively larger size, such ascomposite rotor assembly 11B having end wall 12B. As shown and describedherein, the components comprising embodiment 10 may be utilized to holda workpiece (such as rotor 11A or rotor 11B) such that its end wall ismaintained in a position substantially perpendicular to the axis ofrotation of the shaft. The workpieces illustrated in FIGS. 2 and 3(rotor 11A and rotor 11B) are both of the composite type, wherein theend walls 12A and 12B and their adjacent sidewalls are formed from aseparate, thinner piece of metal from those which form the annulardiscs, although the invention is not limited to use with such types ofworkpieces.

Embodiment 10 includes arbor mount 13 comprising a substantiallycylindrical tube portion 14 having an enlarged terminal member 16 at oneend. Arbor mount 13 also has a central bore 18 therethrough such thatthe axis of the central bore is substantially coincident with the axisof tube portion 14. Central bore 18 of arbor mount 13 is adapted toreceive the shaft of a lathe (not shown) in sliding engagementtherewith. As viewed in FIG. 1, the arbor mount would slide over theouter end of the shaft of a lathe (not shown) in the direction towardsthe extreme lower rightmost corner of the page, and be secured thereonby any convenient means, such as a conventional arbor nut (also notshown). Tube portion 14 has an outside diameter that is smaller than thediameter of the central hole in the end wall of the workpiece to be heldby assembly 10, so as to insure that the tube portion of the assemblywill pass through the central hole in the end wall (not shown in FIG. 1)of a workpiece to be held in place on the shaft of a lathe. Preferably,tube portion 14 of arbor mount 13 has an outside diameter that is withinthe range of about 1.75 to about 2.00 inches. Arbor mount 13 may beidentical to the center locator that is manufactured and sold by RELSManufacturing Company for use with its mounting systems for hublessdrums and hubless rotors.

Assembly 10 also includes first backing plate 20 having a first side 22and a second side 24 and a central hole 26 therethrough, which hole hasa diameter that is larger than the outside diameter of the tube portionof the arbor mount, so that tube portion 14 will pass through hole 26.On first side 22 of first backing plate 20 is located a central recess28 around hole 26, which recess is adapted to receive in matingrelationship terminal member 16 of arbor mount 13. Preferably, terminalmember 16 and recess 28 are substantially circular, although they may beof any convenient shape. In addition, it is preferred that the firstbacking plate have an outside diameter of about 5.00 inches.

Assembly 10 also includes first centering cone 30 having a larger end 32and a smaller end 34 and a central bore 36 therethrough such that theaxis of the central bore is substantially coincident with the axis ofthe cone. Central bore 36 of cone 30 is adapted to receive the tubeportion of the arbor mount in sliding engagement therewith. Cone 30 maybe identical to the cone that is manufactured and sold by RELSManufacturing Company for use with its mounting system for hubless drumsand hubless, unitary rotors. It has a diameter at larger end 32 that islarger than the diameter of central hole 26 in backing plate 20, andlarger than the diameter of the central hole in the end wall of theworkpiece. Preferably, first centering cone 30 has a diameter at itslarger end that is about 3.5 inches. First centering cone 30 also has adiameter at its smaller end 34 that is smaller than the diameter ofcentral hole 26 in backing plate 20.

Preferably, first backing plate 20 has on its second side a beveledsurface 38 extending radially outwardly from central hole 26, andterminal member 16 of arbor mount 13 is provided with a beveled surface40 that is substantially parallel to and in alignment with beveledsurface 38.

The provision of these beveled surfaces will accommodate the cone andwill allow it to protrude further into the central hole than wouldotherwise be possible. This increases the flexibility of the system andpermits its use in connection with workpieces having central holes ofvarious sizes in their end walls. An examination of FIGS. 2 and 3 willshow how the invention may be used to hold workpieces having centralholes of different sizes in their end walls. FIG. 2 illustrates how theinvention may be used to hold workpiece 11A, having a central hole inits end wall 12A that has a smaller diameter than that of the centralhole in first backing plate 20.

FIG. 3, on the other hand, illustrates how the invention may be used tohold workpiece 11B, having a central hole in its end wall 12B that has alarger diameter than that of the central hole in first backing plate 20.As used herein, "the diameter of the central hole in first backing plate20" refers to the diameter at the innermost edge of beveled surface 38.

Preferred results have been obtained when the angle of the beveledsurface extending radially outwardly from the central hole in the secondside of the backing plate is within the range of about 40 to about 50degrees, and most preferably about 45 degrees. It is also preferred thatthe angle of the beveled surface in the terminal member match orcorrespond with the angle of the beveled surface in the backing plate.Furthermore, it is also preferred that the cone comprise a portion of aright circular cone, and that the angle between the axis of the cone andthe conical surface 42 substantially corresponds to the angle of thebeveled surface in the backing plate. These preferred configurationswill allow the cone, the backing plate and the arbor mount to beutilized to hold a workpiece having a relatively large central hole inits end wall, such as is illustrated in FIG. 3. Furthermore, thesepreferred configurations will allow more contact between bevelledsurfaces 38 and 40 and conical surface 42 in such circumstance, whichwill increase the stability of the workpiece mount.

Assembly 10 also includes compression cup 44 having a base portion 46with central hole 48 therethrough, which is adapted to receive tubeportion 14 of arbor mount 13. Compression cup 44 is also provided withsidewall 50 extending from the periphery of the base portion. Thissidewall terminates in a peripheral edge 52 that is located so as tocorrespond with the periphery of the first backing plate. This alignmentof peripheral edge 52 and the periphery of the first backing plate, withend wall 12A (FIG. 2) or 12B (FIG. 3) of the workpiece therebetween,permits compression cup 44 to be utilized to apply compressive forces tothe end wall of the workpiece at locations away from its central hole.Preferably, as shown in the drawings, first backing plate 20 is providedwith a raised edge portion 54 around the periphery thereof, andperipheral edge 52 of the sidewall of the compression cup is located soas to correspond with said raised edge portion. This configuration ofthe components of the invention permits the application of compressiveforces substantially all of the way around the end wall off theworkpiece, and it also permits the compressive forces to be confined tothe area of the end wall of the workpiece between edge 52 and portion54, so that the compressive force per unit area may thereby beincreased. In use, as shown in FIGS. 2 and 3, compression cup 44 ispositioned and secured by any convenient means over the arbor mount insuch fashion that compressive forces may be applied to the end wall ofthe workpiece between the peripheral edge of the sidewall of the cup andthe periphery of the backing plate. Preferably, the end of tube portion14 of the arbor mount opposite terminal member 16, identified in thedrawings as end 56, is provided with external threads so that nut 58 maybe utilized to secure the compression cup over the arbor mount andagainst the end wall of the workpiece. As nut 58 is tightened down onassembly 10, compressive forces will be applied to the end wall of theworkpiece. Since nut 58 is tightened onto the arbor mount instead ofonto the arbor or shaft itself, there is no risk of overtightening thatcould warp the shaft, as may occur when bell clamps are secured on theshaft by the arbor nut.

The invention also contemplates that spacer 60, having a holetherethrough that is adapted to receive the tube portion of the arbormount, may be placed over the arbor mount between the compression cupand the nut, if required to insure that nut 58 may engage the threads onend 56 of the tube portion of arbor mount 13 to apply a compressiveforce to the end wall of the workpiece. Spacer 60 and nut 58 may also beprovided in a single, unitary piece, if desired, although such anembodiment is not illustrated in the drawings.

The invention also provides for holding the cone securely against theend wall of the workpiece at its central hole. This will insure that theworkpiece is properly aligned on the arbor mount. The cone may be heldin such secure position by the provision of a tight frictional fitbetween the cone and the tube portion of the arbor mount, or by means ofthe use of an additional component in the assembly. Such additionalcomponents may comprise a spring, or one or more spring-like metal clipsor the like (not shown) that may be placed inside the cup so that theinside of base portion 46 will compress the spring (or other component)against the larger end of the cone. If such additional components areemployed, they will serve to apply a force to the end wall of theworkpiece that will supplement that provided by the compression cup.

Preferred results may be obtained if the compression cup is providedwith a spring, such as spring 62 (not shown in FIG. 1), that is adaptedto bear against the larger end of the first cone so as to maintain thecone in position against the end wall of the workpiece. Spring 62 may bepermanently attached to the inside of base portion 46 of compression cup44, if desired, by any convenient means, such as by welding or by theuse of mechanical retaining clips (not shown). In addition, the portionof the spring that is in contact with the inside of base portion 46 ofcompression cup 44 may be received in a groove that is cut into theinside of base portion 46, although such embodiment of the invention isnot illustrated in the drawings. In such case, the spring may bemaintained in place inside the cup by one or more screws (not shown)that are located beside the spring groove and disposed to hold thespring securely therein.

As mentioned previously, FIG. 3 illustrates how the invention may beused to hold workpiece 11B, having a central hole in its end wall 12Bthat has a larger diameter than that of the central hole in firstbacking plate 20. If end wall 12B is very thin, the application ofcompressive force thereto according to the invention may cause someelastic deflection in the end wall, although such is not shown in thedrawing. Such deflection may be accommodated by the difference inelevation between the main portion of the second side 24 of the firstbacking plate and raised portion 54 around the periphery thereof.

FIGS. 4 and 5 illustrate a second embodiment of components of the kitthat may be employed to secure larger workpieces of unitaryconstruction, such as for example, the larger components of a "superduty" braking system, on a lathe. Such workpieces are less likely toexhibit "chattering" when mounted on a lathe than are workpieces ofcomposite construction. However, most of the components of the kitillustrated in FIGS. 4 and 5 are the same components As are used in theconfiguration of FIGS. 1 through 3. Thus, for example, embodiment 110includes arbor mount 13 comprising a substantially cylindrical tubeportion 14 having an enlarged terminal member 16 at one end. Arbor mount13 also has a central bore 18 therethrough such that the axis of thecentral bore is substantially coincident with the axis of tube portion14.

Central bore 18 of arbor mount 13 is adapted to receive the shaft of alathe (not shown) in sliding engagement therewith. As viewed in FIG. 4,the arbor mount would slide over the outer end of the shaft of a lathe(not shown) in the direction towards the extreme lower rightmost cornerof the page, and be secured thereon by any convenient means, such as aconventional arbor nut (also not shown). Tube portion 14 has an outsidediameter that is smaller than the diameter of the central hole in theend wall of the workpiece to be held by assembly 110, so as to insurethat the tube portion of the assembly will pass through the central holein the end wall (not shown in FIG. 4) of a workpiece to be held in placeon the shaft of a lathe.

Assembly 110 also includes second backing plate 120 having a first side122 and a second side 124 and a central hole 126 therethrough, whichhole has a diameter that is larger than the outside diameter of the tubeportion of the arbor mount, so that tube portion 14 will pass throughhole 126. Second backing plate 120 has a generally circularconfiguration with an outside diameter greater than that of the firstbacking plate. Furthermore, as illustrated by comparing FIGS. 2 and 5,backing plate 120 is preferably thicker than first backing plate 20 in adirection parallel (in FIGS. 2 and 5) to the axis of tube portion 14.Preferably, second backing plate 120 has an outside diameter of about7.50 inches and a thickness of about 1.75 inches. In addition, backingplate 120 is preferably provided with a larger edge portion 154 (ascompared to edge portion 54 of plate 20) around its periphery, forbearing against and supporting the end wall 112 of the workpiece. Onfirst side 122 of second backing plate 120 is located a central recess128 around hole 126, which recess is adapted to receive in matingrelationship terminal member 16 of arbor mount 13. Preferably, terminalmember 16 and recess 128 are substantially circular, although they maybe of any convenient shape.

Assembly 110 also includes second centering cone 130 having a larger end132 and a smaller end 134 and a central bore 136 therethrough such thatthe axis of the central bore is substantially coincident with the axisof the cone. Central bore 136 of cone 130 is adapted to receive the tubeportion of the arbor mount in sliding engagement therewith. Cone 130 hasa diameter at larger end 132 that is larger than the diameter at largerend 32 of cone 30. In addition, cone 130 has a diameter at larger end132 that is larger than the diameter of central hole 126 in secondbacking plate 120, and larger than the diameter of the central hole inthe end wall of the workpiece. Preferably, the second centering cone hasa diameter at its larger end that is about

5.5 inches. It also has a diameter at its smaller end 134 that issmaller than the diameter of central hole 126 in backing plate 120.

Preferably, second backing plate 120, like first backing plate 20, hason its second side a beveled surface 138 extending radially outwardlyfrom central hole 126, and terminal member 16 of arbor mount 13 isprovided with a beveled surface 40 that is substantially parallel to andin alignment with beveled surface 138. The provision of these beveledsurfaces will accommodate the cone and will allow it to protrude furtherinto the central hole than would otherwise be possible. This increasesthe flexibility of the system and permits its use in connection withworkpieces having central holes of various sizes in their end walls.FIGS. 4 and 5 illustrate how the invention may be used to hold aworkpiece of unitary construction, having a central hole of relativelylarge size in its end wall 112, on a lathe.

Preferred results have been obtained when the angle of the beveledsurface extending radially outwardly from the central hole in the secondside of the backing plate is within the range of about 40 to about 50degrees, and most preferably about 45 degrees. It is also preferred thatthe angle of the beveled surface in the terminal member match orcorrespond with the angle of the beveled surface in the backing plate.Furthermore, it is also preferred that the second cone comprise aportion of a right circular cone, and that the angle between the axis ofcone 130 and the conical surface 142 substantially corresponds to theangle of the beveled surface in the backing plate. These preferredconfigurations will allow the cone, the backing plate and the arbormount to be utilized to hold a workpiece having a relatively largecentral hole in its end wall. Furthermore, these preferredconfigurations will allow more contact between bevelled surfaces 138 and40 and conical surface 142 in such circumstance, which will increase thestability of the workpiece mount.

The invention also provides for holding the cone securely against theend wall of the workpiece at its central hole. Preferably, the end oftube portion 14 of the arbor mount opposite terminal member 16,identified in the drawings as end 56, is provided with external threadsso that nut 58 may be utilized to secure the second centering coneagainst the end wall of the workpiece. As nut 58 is tightened down onassembly 10, compressive forces will be applied to the end wall of theworkpiece. Since nut 58 is tightened onto the arbor mount instead ofonto the arbor or shaft itself, there is no risk of overtightening thatcould warp the shaft, as may occur when bell clamps are secured on theshaft by the arbor nut. The invention also contemplates that spacer 60,having a hole therethrough that is adapted to receive the tube portionof the arbor mount, may be placed over the arbor mount between thesecond centering cone and the nut, if required to insure that nut 58 mayengage the threads on end 56 of the tube portion of arbor mount 13 toapply a compressive force to the end wall of the workpiece. Spacer 60and nut 58 may also be provided in a single, unitary piece, if desired,although such an embodiment is not illustrated in the drawings. It isnot generally considered to be necessary to employ compression cup 44 inconnection with workpieces of unitary construction. However, if sodesired or if larger workpieces of composite construction areencountered, compression cup 44 may also be sized large enough to fitover second cone 130, or the kit may be provided with a secondcompression cup (not shown) that is larger than cup 44 and sized so thatits peripheral edge is located so as to correspond with edge portion 154of plate 120. If so, the compression cup may be employed to applycompressive forces to end wall 112 of the workpiece at locations awayfrom its central hole. In such case, it may be necessary or desirable toomit spacer 60 before securing compression cup over cone 130 and againstthe workpiece, or to employ an arbor mount having a longer tube portion14.

As described herein, the invention may be suitable for holdingworkpieces such as brake drums and rotors on the shaft of a rotarydriven lathe for machining, regardless of whether the workpieces are ofunitary or composite construction. The invention may also hold suchworkpieces having central holes in their end walls that vary in diameterover a relatively wide range. When the kit of the invention includes apair of backing plates and a pair of centering cones, one pair sized formost automobiles and light trucks, and the other sized for trucks having"super duty" braking systems, most of the brake drums and rotors likelyto be encountered can be resurfaced. It may also be desirable to includea third backing plate, similar in configuration to the first but havingan outside diameter larger than that of the first backing plate butsmaller than that of the second, in the kit. This third plate, ifprovided, could be used in cooperation with either the first or thesecond cones. The second compression cup (described herein for use inconnection with backing plate 120) could readily be sized so as to beused in cooperation with either the second or third backing plate. Suchan assembly, including the third backing plate, a second compression cupand either the first or second cone, could be used to mount drums androtors of trucks having brake components larger than those of mostautomobiles and light trucks but smaller than those with super dutybraking systems. If the standard RELS system components are used as thearbor mount, first centering cone, spacer and nut, the invention can beutilized to machine brake drums and rotors that are commonly used onnearly all automobiles, as well as on most trucks up to about a 2-toncapacity.

Although this description contains many specifics, these should not beconstrued as limiting the scope of the invention but as merely providingillustrations of some of the presently preferred embodiments thereof, aswell as the best mode contemplated by the inventor for carrying out theinvention. The invention, as described herein, is susceptible to variousmodifications and adaptations, and the same are intended to becomprehended within the meaning and range of equivalents of the appendedclaims.

What is claimed is:
 1. A kit of components for use in attaching andsecuring workpieces on a lathe having a rotary driven shaft, saidworkpieces comprising hubless brake drums and rotors of various sizes,each of which is provided with an end wall with a central hole therein,said kit being adapted to attach and secure said workpieces in a mannersuch that said end wall is maintained in a position substantiallyperpendicular to the axis of rotation of the shaft, said kitcomprising:(a) an arbor mount comprising a substantially cylindricaltube portion with an enlarged terminal member at one end thereof, saidarbor mount having a central bore therethrough such that the axis of thecentral bore of the arbor mount is substantially coincident with theaxis of the tube portion, said central bore of the arbor mount beingadapted to receive the shaft in sliding engagement therewith so thatsaid arbor mount may be positioned over the shaft; (b) a first backingplate having a generally circular configuration with a first side and asecond side and a central hole therethrough, which hole has a diameterthat is greater than the outside diameter of the tube portion of thearbor mount so that said tube portion will pass through the central holeof the first backing plate, said first side of said first backing platebeing adapted to receive in mating relationship the terminal member ofthe arbor mount, said first backing plate being adapted to be positionedover the tube portion of the arbor mount in mating relationship with theterminal member thereof, behind a workpiece; (c) a second backing platehaving a generally circular configuration with an outside diametergreater than that of the first backing plate, said second backing platehaving a first side and a second side and a central hole therethrough,which hole has a diameter that is greater than the outside diameter ofthe tube portion of the arbor mount so that said tube portion will passthrough the central hole of the second backing plate, said first side ofsaid second backing plate being adapted to receive in matingrelationship the terminal member of the arbor mount, said second backingplate being adapted to be positioned over the tube portion of the arbormount in mating relationship with the terminal member thereof, behind aworkpiece; (d) a first centering cone having a larger end and a smallerend, and having a central bore therethrough such that the axis of thecentral bore of said first centering cone is substantially coincidentwith the axis of the cone, said bore of the first centering cone beingadapted to receive the tube portion of the arbor mount in slidingengagement therewith, said first centering cone being adapted to bepositioned over the tube portion of the arbor mount with its smaller endpreceding its larger end and secured against the end wall of aworkpiece; (e) a second centering cone having a larger end and a smallerend, and having a central bore therethrough such that the axis of thecentral bore of said second centering cone is substantially coincidentwith the axis of the cone, said bore of the second centering cone beingadapted to receive the tube portion of the arbor mount in slidingengagement therewith, said second centering cone having a diameter atits larger end that is greater than the diameter at the larger end ofthe first centering cone, said second centering cone being adapted tothe positioned over the tube portion of the arbor mount with its smallerend preceding its larger end and secured against the end wall of aworkpiece; (f) means for securing a centering cone on the tube portionof the arbor mount against the end wall of a workpiece; (g) acompression cup having a base portion and a sidewall extending from theperiphery thereof, said base portion having a central hole therethroughthat is adapted to receive the tube portion of the arbor mount, and saidsidewall terminating in a peripheral edge that is located so as tocorrespond with the periphery of the first backing plate, saidcompression cup being adapted to be positioned and secured over thearbor mount so that compressive forces may be applied to the end wall ofa workpiece between the peripheral edge of the sidewall of the cup andthe periphery of the first backing plate; (h) means for securing thecompression cup over the arbor mount.
 2. The kit of claim 1 wherein atleast a part of the tube portion of the arbor mount away from theterminal member is provided with external threads, and wherein the kitalso includes a nut having internal threads that are adapted to matewith the external threads of the tube portion, said nut being adaptedfor securing a centering cone on the tube portion of the arbor mountagainst the end wall of a workpiece or for securing the compression cupover the arbor mount.
 3. The kit of claim 2 wherein a spacer, having ahole therethrough that is adapted to receive the tube portion of thearbor mount, is provided for placement over the arbor mount between thenut and the base of a cone or between the compression cup and the nut.4. The kit of claim 2 wherein the nut is provided with a unitary spacerportion.
 5. The kit of claim 1 wherein the tube portion of the arbormount has an outside diameter that is within the range of about 1.75 to2.00 inches.
 6. The kit of claim 1 wherein the first backing plate hasan outside diameter of about 5.00 inches.
 7. The kit of claim 1 whereinthe first backing plate is provided with a raised portion around theperiphery thereof, and wherein the sidewall of the compression cupterminates in a peripheral edge that is located so as to correspond withsaid raised portion.
 8. The kit of claim 1 wherein the second backingplate has a thickness that is greater than that of the first backingplate.
 9. The kit of claim 1 wherein the second backing plate isprovided with an edge portion around its periphery that is larger thanthe edge portion of the first backing plate, which edge portion isadapted for bearing against the end wall of the workpiece.
 10. The kitof claim 1 wherein the first centering cone has a diameter at its largerend of about 3.50 inches.
 11. The kit of claim 1 wherein the secondcentering cone has a diameter at its larger end of about 5.50 inches.12. The kit of claim 1 wherein the terminal member of the arbor mount isprovided with a beveled surface extending from the juncture of the tubeportion and the terminal member radially outwardly and axially towardsthe opposite end of the tube portion, and wherein the second side ofeach of the first and second backing plates is provided with a beveledsurface that is substantially parallel to and in alignment with thebeveled surface of the terminal member.
 13. The kit of claim 12 whereinthe angle of the beveled surfaces is within the range of about 40 toabout 50 degrees.
 14. The kit of claim 12 wherein the first centeringcone comprises a portion of a right circular cone, and wherein the anglebetween the axis of the first centering cone and the conical surfacethereof substantially corresponds to the angle of the beveled surfaces.15. The kit of claim 12 wherein the second centering cone comprises aportion of a light circular cone, and wherein the angle between the axisof the second centering cone and the conical surface thereofsubstantially corresponds to the angle of the beveled surfaces.
 16. Thekit of claim 1 wherein at least a part of the means for securing thefirst centering cone against the end wall of a workpiece comprises aspring that is adapted to be compressed between the inside of thecompression cup and the larger end of the first centering cone.
 17. Thekit of claim 16 wherein the compression cup is provided with an integralspring that is adapted to bear against the larger end of a centeringcone so that the cup may be used to secure said cone in position againstthe end wall of a workpiece.
 18. The kit of claim 1 wherein the firstside of each of said backing plates is provided with a central recessthat is adapted to receive in mating relationship the terminal member ofthe arbor mount.
 19. The kit of claim 18 wherein each of the centralrecesses is substantially circular.